BBufferedDataIO: Fix Write().

I looked at this code as a reference when writing similar code in another
project, and realized then that this was broken to the point where I
don't think anyone could have actually used it:

1. Writes larger than the buffer should only return the amount written
by this Write() call, not the amount flushed beforehand.

2. fDirty was only set if there were bytes remaining after the first
write to the buffer. So, if you wrote small amounts of data, they
would be silently discarded most of the time!

3. When filling the buffer, we might as well flush simultaneously.
This allows the logic to be consolidated into a loop and remove the
duplicate memcpy. In case of failure, just return the bytes-written
as the write could be retried later.

4. Flush() should always return an error or 0, not bytes written.

While at it, add some basic tests for this class.

Change-Id: I2de01d0b31e3fe22863cef21dd7b0b62ed47121b

src/kits/support/BufferedDataIO.cpp

@@ -95,10 +95,10 @@ BBufferedDataIO::Flush()
 	} else if (bytesWritten >= 0) {
 		fSize -= bytesWritten;
 		fPosition += bytesWritten;
-		return B_ERROR;
+		return B_PARTIAL_WRITE;
 	}
 
-	return bytesWritten;
+	return B_OK;
 }
 
 
@@ -172,6 +172,15 @@ BBufferedDataIO::Write(const void* buffer, size_t size)
 
 	TRACE("%p::Write(size %lu)\n", this, size);
 
+	if (size > fBufferSize || fBuffer == NULL) {
+		// request is larger than our buffer, just fill it directly
+		status_t status = Flush();
+		if (status != B_OK)
+			return status;
+
+		return fStream.Write(buffer, size);
+	}
+
 	if (!fDirty) {
 		// Throw away a read-only buffer if necessary
 		TRACE("%p: throw away previous buffer.\n", this);
@@ -180,39 +189,21 @@ BBufferedDataIO::Write(const void* buffer, size_t size)
 	}
 
 	size_t bytesWritten = 0;
-
-	if (size > fBufferSize || fBuffer == NULL) {
-		// request is larger than our buffer, just fill it directly
-		bytesWritten = fSize;
-
-		status_t status = Flush();
-		if (status != B_OK)
-			return status;
-
-		ssize_t streamWritten = fStream.Write(buffer, size);
-		if (streamWritten >= 0)
-			return bytesWritten + streamWritten;
-
-		return streamWritten;
-	}
-
-	bytesWritten = min_c(size, fBufferSize - fSize - fPosition);
-	TRACE("%p: write %" B_PRIuSIZE " bytes to the buffer.\n", this,
-		bytesWritten);
-	memcpy(fBuffer + fPosition + fSize, buffer, bytesWritten);
-	fSize += bytesWritten;
-	size -= bytesWritten;
-
-	if (size > 0) {
-		status_t status = Flush();
-		if (status != B_OK)
-			return status;
-
-		memcpy(fBuffer, (uint8*)buffer + bytesWritten, size);
-		fPosition = 0;
-		fSize = size;
+	while (size > 0) {
+		size_t toCopy = min_c(size, fBufferSize - (fPosition + fSize));
+		TRACE("%p: write %" B_PRIuSIZE " bytes to the buffer.\n", this,
+			toCopy);
+		memcpy(fBuffer + (fPosition + fSize), buffer, toCopy);
+		fSize += toCopy;
+		bytesWritten += toCopy;
+		size -= toCopy;
 		fDirty = true;
-		bytesWritten += size;
+
+		if ((fPosition + fSize) == fBufferSize) {
+			status_t status = Flush();
+			if (status != B_OK)
+				return bytesWritten;
+		}
 	}
 
 	return bytesWritten;

src/tests/kits/storage/DataIOTest.cpp

@@ -0,0 +1,46 @@
+// DataIOTest.cpp
+
+#include <string.h>
+#include <BufferedDataIO.h>
+
+#include <TestShell.h>
+
+#include "DataIOTest.h"
+
+
+CppUnit::Test*
+DataIOTest::Suite() {
+	CppUnit::TestSuite *suite = new CppUnit::TestSuite();
+	typedef CppUnit::TestCaller<DataIOTest> TC;
+
+	suite->addTest(new TC("BResourceString::BufferedDataIO Test",
+		&DataIOTest::BufferedDataIOTest));
+
+	return suite;
+}
+
+
+void
+DataIOTest::BufferedDataIOTest()
+{
+	// very basic test
+	NextSubTest();
+	{
+		BMallocIO mallocIO;
+		CPPUNIT_ASSERT(mallocIO.SetSize(1024) == B_OK);
+
+		BBufferedDataIO bufferedDataIO(mallocIO, 8, false);
+		CPPUNIT_ASSERT(bufferedDataIO.InitCheck() == B_OK);
+
+		CPPUNIT_ASSERT(bufferedDataIO.Write("test ", 5) == 5);
+		CPPUNIT_ASSERT(bufferedDataIO.Write("test ", 5) == 5);
+		CPPUNIT_ASSERT(bufferedDataIO.Write("test ", 5) == 5);
+
+		CPPUNIT_ASSERT(bufferedDataIO.Flush() == B_OK);
+
+		CPPUNIT_ASSERT(bufferedDataIO.Write("longer-test", 12) == 12);
+
+		CPPUNIT_ASSERT(mallocIO.Position() == 27);
+		CPPUNIT_ASSERT(memcmp(mallocIO.Buffer(), "test test test longer-test", 27) == 0);
+	}
+}

src/tests/kits/storage/DataIOTest.h

@@ -0,0 +1,23 @@
+// DataIOTest.h
+
+#ifndef __sk_data_io_test_h__
+#define __sk_data_io_test_h__
+
+#include <cppunit/TestCaller.h>
+#include <cppunit/TestSuite.h>
+
+#include <StorageDefs.h>
+#include <SupportDefs.h>
+
+#include "BasicTest.h"
+
+class DataIOTest : public BasicTest
+{
+public:
+	static CppUnit::Test* Suite();
+
+	void BufferedDataIOTest();
+};
+
+
+#endif	// __sk_data_io_test_h__

src/tests/kits/storage/Jamfile

@@ -8,6 +8,7 @@ UnitTestLib libstoragetest.so
 	: StorageKitTestAddon.cpp
 		AppFileInfoTest.cpp
 		BasicTest.cpp
+		DataIOTest.cpp
 		DirectoryTest.cpp
 		EntryTest.cpp
 		FindDirectoryTest.cpp

src/tests/kits/storage/StorageKitTestAddon.cpp

@@ -4,6 +4,7 @@
 // ##### Include headers for your tests here #####
 #include "AppFileInfoTest.h"
 #include "DirectoryTest.h"
+#include "DataIOTest.h"
 #include "EntryTest.h"
 #include "FileTest.h"
 #include "FindDirectoryTest.h"
@@ -24,6 +25,7 @@ BTestSuite* getTestSuite() {
 	// ##### Add test suites here #####
 	suite->addTest("BAppFileInfo", AppFileInfoTest::Suite());
 	suite->addTest("BDirectory", DirectoryTest::Suite());
+	suite->addTest("BDataIO", DataIOTest::Suite());
 	suite->addTest("BEntry", EntryTest::Suite());
 	suite->addTest("BFile", FileTest::Suite());
 #if 0